/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.lang.model;

import java.util.Collections;
import java.util.Set;
import java.util.HashSet;

/**
 * Source versions of the Java&trade; programming language.
 *
 * See the appropriate edition of
 * <cite>The Java&trade; Language Specification</cite>
 * for information about a particular source version.
 *
 * <p>Note that additional source version constants will be added to
 * model future releases of the language.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @since 1.6
 */
public enum SourceVersion {
    /*
     * Summary of language evolution
     * 1.1: nested classes
     * 1.2: strictfp
     * 1.3: no changes
     * 1.4: assert
     * 1.5: annotations, generics, autoboxing, var-args...
     * 1.6: no changes
     * 1.7: diamond syntax, try-with-resources, etc.
     * 1.8: lambda expressions and default methods
     */

  /**
   * The original version.
   *
   * The language described in
   * <cite>The Java&trade; Language Specification, First Edition</cite>.
   */
  RELEASE_0,

  /**
   * The version recognized by the Java Platform 1.1.
   *
   * The language is {@code RELEASE_0} augmented with nested classes as described in the 1.1 update
   * to <cite>The Java&trade; Language Specification, First Edition</cite>.
   */
  RELEASE_1,

  /**
   * The version recognized by the Java 2 Platform, Standard Edition,
   * v 1.2.
   *
   * The language described in
   * <cite>The Java&trade; Language Specification,
   * Second Edition</cite>, which includes the {@code
   * strictfp} modifier.
   */
  RELEASE_2,

  /**
   * The version recognized by the Java 2 Platform, Standard Edition,
   * v 1.3.
   *
   * No major changes from {@code RELEASE_2}.
   */
  RELEASE_3,

  /**
   * The version recognized by the Java 2 Platform, Standard Edition,
   * v 1.4.
   *
   * Added a simple assertion facility.
   */
  RELEASE_4,

  /**
   * The version recognized by the Java 2 Platform, Standard
   * Edition 5.0.
   *
   * The language described in
   * <cite>The Java&trade; Language Specification,
   * Third Edition</cite>.  First release to support
   * generics, annotations, autoboxing, var-args, enhanced {@code
   * for} loop, and hexadecimal floating-point literals.
   */
  RELEASE_5,

  /**
   * The version recognized by the Java Platform, Standard Edition
   * 6.
   *
   * No major changes from {@code RELEASE_5}.
   */
  RELEASE_6,

  /**
   * The version recognized by the Java Platform, Standard Edition
   * 7.
   *
   * Additions in this release include, diamond syntax for
   * constructors, {@code try}-with-resources, strings in switch,
   * binary literals, and multi-catch.
   *
   * @since 1.7
   */
  RELEASE_7,

  /**
   * The version recognized by the Java Platform, Standard Edition
   * 8.
   *
   * Additions in this release include lambda expressions and default methods.
   *
   * @since 1.8
   */
  RELEASE_8;

  // Note that when adding constants for newer releases, the
  // behavior of latest() and latestSupported() must be updated too.

  /**
   * Returns the latest source version that can be modeled.
   *
   * @return the latest source version that can be modeled
   */
  public static SourceVersion latest() {
    return RELEASE_8;
  }

  private static final SourceVersion latestSupported = getLatestSupported();

  private static SourceVersion getLatestSupported() {
    try {
      String specVersion = System.getProperty("java.specification.version");

      if ("1.8".equals(specVersion)) {
        return RELEASE_8;
      } else if ("1.7".equals(specVersion)) {
        return RELEASE_7;
      } else if ("1.6".equals(specVersion)) {
        return RELEASE_6;
      }
    } catch (SecurityException se) {
    }

    return RELEASE_5;
  }

  /**
   * Returns the latest source version fully supported by the
   * current execution environment.  {@code RELEASE_5} or later must
   * be returned.
   *
   * @return the latest source version that is fully supported
   */
  public static SourceVersion latestSupported() {
    return latestSupported;
  }

  /**
   * Returns whether or not {@code name} is a syntactically valid
   * identifier (simple name) or keyword in the latest source
   * version.  The method returns {@code true} if the name consists
   * of an initial character for which {@link
   * Character#isJavaIdentifierStart(int)} returns {@code true},
   * followed only by characters for which {@link
   * Character#isJavaIdentifierPart(int)} returns {@code true}.
   * This pattern matches regular identifiers, keywords, and the
   * literals {@code "true"}, {@code "false"}, and {@code "null"}.
   * The method returns {@code false} for all other strings.
   *
   * @param name the string to check
   * @return {@code true} if this string is a syntactically valid identifier or keyword, {@code
   * false} otherwise.
   */
  public static boolean isIdentifier(CharSequence name) {
    String id = name.toString();

    if (id.length() == 0) {
      return false;
    }
    int cp = id.codePointAt(0);
    if (!Character.isJavaIdentifierStart(cp)) {
      return false;
    }
    for (int i = Character.charCount(cp);
        i < id.length();
        i += Character.charCount(cp)) {
      cp = id.codePointAt(i);
      if (!Character.isJavaIdentifierPart(cp)) {
        return false;
      }
    }
    return true;
  }

  /**
   * Returns whether or not {@code name} is a syntactically valid
   * qualified name in the latest source version.  Unlike {@link
   * #isIdentifier isIdentifier}, this method returns {@code false}
   * for keywords and literals.
   *
   * @param name the string to check
   * @return {@code true} if this string is a syntactically valid name, {@code false} otherwise.
   * @jls 6.2 Names and Identifiers
   */
  public static boolean isName(CharSequence name) {
    String id = name.toString();

    for (String s : id.split("\\.", -1)) {
      if (!isIdentifier(s) || isKeyword(s)) {
        return false;
      }
    }
    return true;
  }

  private final static Set<String> keywords;

  static {
    Set<String> s = new HashSet<String>();
    String[] kws = {
        "abstract", "continue", "for", "new", "switch",
        "assert", "default", "if", "package", "synchronized",
        "boolean", "do", "goto", "private", "this",
        "break", "double", "implements", "protected", "throw",
        "byte", "else", "import", "public", "throws",
        "case", "enum", "instanceof", "return", "transient",
        "catch", "extends", "int", "short", "try",
        "char", "final", "interface", "static", "void",
        "class", "finally", "long", "strictfp", "volatile",
        "const", "float", "native", "super", "while",
        // literals
        "null", "true", "false"
    };
    for (String kw : kws) {
      s.add(kw);
    }
    keywords = Collections.unmodifiableSet(s);
  }

  /**
   * Returns whether or not {@code s} is a keyword or literal in the
   * latest source version.
   *
   * @param s the string to check
   * @return {@code true} if {@code s} is a keyword or literal, {@code false} otherwise.
   */
  public static boolean isKeyword(CharSequence s) {
    String keywordOrLiteral = s.toString();
    return keywords.contains(keywordOrLiteral);
  }
}
